This invention relates in general to a loudspeaker and in particular to a loudspeaker having a centering device.
A loudspeaker has a diaphragm with an edge area and a central area. A voice coil carrier is fastened to the diaphragm in the central area, a voice coil being wound around the voice coil carrier. A magnet system is included into which the voice coil carrier and the voice coil are completely or partially inserted. A basket encloses one face of the diaphragm and to which the magnet system is fastened. An elastic bead is fastened to the edge area of the diaphragm and to the basket. A centering device is fastened to the central area of the diaphragm and to the basket.
Such a loudspeaker is disclosed, for example, by Ivar Veit, Technische Akustik [Industrial Acoustics], second edition 1978, page 91, where a centering spider fastened to the basket and diaphragm is provided as a centering device. The current in the voice coil and the magnetic field in the air gap of the magnet system interact with one another in such a way that Lorentz forces occur in the direction of the axis of symmetry. This converts the input voltage on the voice coil into a mechanical motion of the voice coil and accordingly of the diaphragm. The suspension of the oscillating system comprising the bead and the centering spider then generates return forces and holds in position the voice coil, which is connected to the radiating diaphragm. Damping then occurs in this oscillating overall system from a suspension comprising electrically the magnet system and mechanically the bead and the centering spider.
Since the magnetic force and hence the electrical damping are not constant in the operating area of the loudspeaker in standard loudspeakers, there is a resultant excursion-dependent overall damping that becomes weaker at large excursions. Designs that avoid this are in general large and uneconomical to manufacture because of the large winding widths and strong magnets needed.
For this reason it is necessary to increase the mechanical damping, which results in the variation of the overall damping becoming smaller. Also, the material and mode of motion of the centering spider cause it to contribute an insignificant component to the overall damping, in particular because of flexing in the edge area and stretching in the principal area.
What is needed is a loudspeaker with increased mechanical damping.